1. Eastern Mediterranean University School of Computing and Technology Department of Information Technology ITEC229 Client-Side Internet and Web Programming Conditional Statements & Loops in JavaScript CHAPTER 10

2. CONTENT 10.1 Conditional Statements • if.. Statement • if.. else Statement • if.. else if Statement • switch case Statement 10.2 Loops • For Loop • While Loop • Do.. While Loop http://sct.emu.edu.tr/it/itec229

3. 10.1 Conditional Statements • Conditional statements are used to perform different actions based on different conditions. • Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this. http://sct.emu.edu.tr/it/itec229

4. 10.1 Conditional Statements In JavaScript we have the following conditional statements: • if statement - use this statement to execute some code only if a specified condition is true • if...else statement - use this statement to execute some code if the condition is true and another code if the condition is false • if...else if....else statement - use this statement to select one of many blocks of code to be executed • switch statement - use this statement to select one of many blocks of code to be executed http://sct.emu.edu.tr/it/itec229

5. 10.1 Conditional Statements if statement: • Use the if statement to execute some code only if a specified condition is true. Syntax: if (condition)  {  code to be executed if condition is true} • Note that if is written in lowercase letters. Using uppercase letters (IF) will generate a JavaScript error! • Notice that there is no ..else.. in this syntax. You tell the browser to execute some code only if the specified condition is true. http://sct.emu.edu.tr/it/itec229

6. 10.1 Conditional Statements if statement: Example: <html><head><title></title></head><body> <script type="text/javascript"> var total=0; var even=0; document.write( "Raygan"); for (x=1; x<=10; x++) { total = total + x; if ((x%2)==0) { even = even + x;} } document.write( "The total sum: "+total+"<br>"); document.write( "The sum of even values:"+ even ); </script></body></html> http://sct.emu.edu.tr/it/itec229

7. 10.1 Conditional Statements if.. elsestatement: Syntax: if (expression) { statement(s) to be executed if expression is true } else { statement(s) to be executed if expression is false } http://sct.emu.edu.tr/it/itec229

8. 10.1 Conditional Statements if.. elsestatement: Example: <script type="text/javascript"> vartotal= prompt("Enter your total", "50"); if (total >=50) {alert("PASSED")} else {alert("FAILED")} </script> http://sct.emu.edu.tr/it/itec229

9. 10.1 Conditional Statements if.. else ifstatement: Syntax: if (expression 1) { statement(s) to be executed if expression 1 is true} else if (expression 2) { statement(s) to be executed if expression 2 is true} else if (expression 3) { statement(s) to be executed if expression 3 is true} else { statement(s) to be executed if no expression is true} http://sct.emu.edu.tr/it/itec229

10. 10.1 Conditional Statements if.. else ifstatement: Example: <script type="text/javascript"> varage = prompt("Enter your age", "25"); if (age >0 && age <= 3) {alert("WOW Baby")} else if (age >= 4 && age < 13) {alert("You are child")} else if (age >= 13 && age < 31) {alert("You are young ;)")} else if (age >= 31 && age < 46) {alert("Middle Age :/")} else if (age >= 46 && age < 71) {alert("You are old :(")} else if (age >= 71 && age < 101) {alert("Get ready for a new world!!!")} else {alert("Ageless")} </script> http://sct.emu.edu.tr/it/itec229

11. 10.1 Conditional Statements switchcase statement: Syntax: switch (expression) { case condition 1: statement(s) break; case condition 2: statement(s) break; ... case condition n: statement(s) break; default: statement(s) } http://sct.emu.edu.tr/it/itec229

12. 10.1 Conditional Statements switchcase statement: Example: <body><script type="text/javascript"> varflower=prompt("Which flower whould you like to buy?","rose"); switch (flower){ case "rose": alert(flower + " costs 10TL"); break; case "daisy": alert(flower + " costs 3TL"); break; case "orchild": alert(flower + " costs 25TL"); break; default: alert("SORRY =( there is no such flower in our shop"); break;} </script> </body> http://sct.emu.edu.tr/it/itec229

13. 10.2 Loops For Loop: For loop is the most compact form of looping and includes the following three important parts: • the loop initialization where we initialize our counter to a starting value. • The initialization statement is executed before the loop begins. • The test statement which will test if the given condition is true or not. If condition is true then code given inside the loop will be executed otherwise loop will come out. • The iteration statement where you can increase or decrease your counter. http://sct.emu.edu.tr/it/itec229

14. 10.2 Loops For Loop: • You can put all the three parts in a single line separated by a semicolon. Syntax: for (initialization; test condition; iteration statement) { statement(s) to be executed if test condition is true } http://sct.emu.edu.tr/it/itec229

15. 10.2 Loops For Loop: Example: <script type="text/javascript"> document.write("<h2>Multiplication table from (1 to 10)</h2>"); document.write("<table border=2 width=50%"); for (vari = 1; i <= 10; i++ ) { //this is the outer loop document.write("<tr>"); document.write("<td>" + i + "</td>"); for ( var j = 2; j <= 10; j++ ) { // inner loop document.write("<td>" + i * j + "</td>"); } document.write("</tr>"); } document.write("</table>"); </script> http://sct.emu.edu.tr/it/itec229

16. 10.2 Loops For Loop: Example Output: http://sct.emu.edu.tr/it/itec229

17. 10.2 Loops The while Loop: •  loops through a block of code as long as a specified condition is true. Syntax: while (condition) { statement(s) to be executed if expression is true } http://sct.emu.edu.tr/it/itec229

18. 10.2 Loops The while Loop: Example: <script type="text/javascript"> vartotal=0; vari=0; varj; while (i<= 10) { j=i%2; if (j!== 0) { total+=i;} i++ } document.write("Total of odd numbers between 1-10:" +" +total); </script> Output: Total of odd numbers between 1-10: 25 http://sct.emu.edu.tr/it/itec229

19. 10.2 Loops The do..while Loop: • similar to the while loop except that the condition check happens at the end of the loop. • this means that the loop will always be executed at least once, even if the condition is false. Syntax: do { statement(s) to be executed; } while (condition); http://sct.emu.edu.tr/it/itec229

20. 10.2 Loops The do..while Loop: Example: <script type="text/javascript"> var num = 0; do{ num = num + 5; document.write(num + "<br />"); } while (num < 25); </script> Output: 5 10 15 20 25 http://sct.emu.edu.tr/it/itec229

21. Thank You ! Conditional Statements & Loops in JavaScript http://sct.emu.edu.tr/it/itec229 END of CHAPTER 10